The present invention relates to nutritional compositions which contain certain classes of non-digestible polysaccharides. These compositions reduce the uptake of high molecular weight substances, allergens and microorganisms through the intestinal wall. In particular the present invention relates to reduction of the free transport of such substances through the tight junctions (TJs) of the intestines, without the transport of low molecular weight substances, such as nutrients, via the intestinal epithelium being impeded. The compositions can be used to prevent the increased permeability of the intestinal wall, due to various causes, and the penetration, resulting therefrom, of toxins, antigens and pathogenic microorganisms present in the lumen.
The structure and fraction of tight junctions is described, inter alia, in Ann. Rev.
Physiol. 60, 121-160 (1998) and in Ballard T. S. et al., Annu.Rev.Nutr., 1995, 15:35-55. Tight junctions do not form a rigid barrier but play an important role in diffusion through the intestinal epithelium from lumen to bloodstream and vice versa.
The permeability of the tight junctions is highly regulated and can be disturbed by disease and certain toxins in the lumen. Regulation takes place from the nervous system, the hormonal system and the immune system. When tight junctions are opened substances having a high molecular weight, allergens and even microorganisms will pass through the tight junctions. The translocation of substances having a high molecular weight can, under certain conditions, give rise to sensitisation of the immune system and result in allergic reactions on a subsequent exposure. Translocation of pathogenic microorganisms makes a substantial call on the immune system and, inter alia in periods of reduced resistance, can make persons and animals ill. The same applies, for example, in the case of bacterial toxins which have been able to pass through the epithelial layer and have been able to reach the bloodstream.
The invention now relates to nutritional compositions which contain slightly negatively charged non-digestible polysaccharides having a molecular weight of 8 kD to 40,000 kD, characterised in that the rise in the viscosity of the composition caused by the polysaccharides is less than 20 mPaxc2x7s.
In particular the invention relates to the use of these compositions to reduce the uptake of high molecular weight substances, allergens and microorganisms through the intestinal wall.
More particularly the invention relates to the use of the abovementioned compositions to reduce transport of high molecular weight substances, allergens and microorganisms through the tight junctions in the intestines.
Some of the polysaccharides described above have already been described previously. U.S. Pat. No. 2,813,797 and U.S. Pat. No. 2,834,684 describe the use of carboxymethyldextran as a thickener, by which means the nutrient acquires certain desirable functional characteristics. This viscosity-raising effect is, as will be described below, undesirable in the case of the present invention.
Furthermore, in WO 97/41899 the thickening action of oxidised dextrans is used to make a wound dressing through which the active components are released in a controlled and slow manner to the tissue located under the dressing.
EP 0 772 446 describes the use of a combination of chitosan and dextran sulphate to prevent damaged tissue undesirably adhering to surrounding tissue. EP 0 759 760 discloses the stimulating action of the combination of chitosan and dextran sulphate on the healing of skin wounds.
In EP 0 754 460 it is described that sulphated acid mucopolysaccharides and dextran sulphate can be used for the treatment of diseases associated with inflammation, such as rheumatoid arthritis, ischaemia of the heart or brain, atopic dermatitis, infiltration following organ transplant.
In EP 0 737 072 it is described that sulphated polysaccharides such as dextran sulphate can prevent binding of bacteria to the wall of the respiratory system. WO 96/30027 discloses that sulphated polysaccharides such as carragheenan and dextran sulphate can be used to combat Rotavirus infections. EP 0 719 783 describes the use of non-digestible highly phosphorylated polysaccharides in nutrients to increase calcium absorption.
None of these documents describes the beneficial effect of slightly negatively charged polysaccharides as defined in claim 1 of this Application. More particularly, it is not described that these polysaccharides have an effect on the tight junctions in the intestines and in the event of disturbance of the permeability of the tight junctions are able to reduce the transport of high molecular weight substances, allergens and microorganisms through the tight junctions into the intestines.
In addition to the significant reduction in the transport of harmful substances and microorganisms, a significant advantage of the present invention is that the normal transport of useful substances (nutrients) such as glucose, amino acids, dipeptides or trace elements is substantially maintained.
According to the invention, non-digestible polysaccharides are understood to be polysaccharides which are not or are barely digested or converted by the human digestive enzymes under the conditions prevailing in the body. It must be pointed out that some of the non-digestible polysaccharides can be fermented by the microorganisms present in the intestines (colon, caecum and part of the ileum). Without wishing to be tied to any theory, it is, however, expected that the effect of the polysaccharides on the paracellular transport does not take place via the fermentation products.
The extent to which the polysaccharides are digested can be determined using the method as described in Minekus, M., Ph.D Thesis, University of Utrecht, 1998, Development and validation of a dynamic model of the gastrointestinal tract, Section 2. The polysaccharides according to the invention are less than 50% and preferably less than 30% digestible.
Preferably, the polysaccharides according to the invention contain groups which are negatively charged at pH 5.5-8, such as carboxyl, sulphate or phosphate, in a quantity of 1 negatively charged group per 3 to 10,000 saccharide units, preferably 1 negatively charged group per 10 to 10,000 saccharide units. Polysaccharides in which the negatively charged groups are carboxyl groups are most preferred.
These polysaccharides can be obtained via a synthesis route or by making use of naturally occurring polysaccharides.
Examples of modified polysaccharides are dextrans into which a negative group has been introduced, for example carboxydextran or carboxymethyldextran. Following or during hydrolysis of a high molecular weight dextran, one or more carboxyl groups can be introduced into the molecule by derivatisation. Derivatisation can, for example, take place by using the Kiliani-Fischer reaction or by carboxymethylation with, for example, chloroacetic acid or by oxidation of, for example, the reducing end of the molecule. Neutral naturally occurring polysaccharides can also be provided with one or more acid groups in this way. Examples of suitable naturally occurring polysaccharides are gluco-mannans; (galacto)mannans, such as guar gum, tara gum, carob gum and locust bean gum; curdlan; agar agar; arabans; (arabino)galactans, tamarind gum, pullulan and (arabino)xylans. Preferably the shortened forms or the hydrolysis products of these polysaccharides are used. Mixtures of modified polysaccharides can also be used.
Naturally occurring polysaccharides such as gum arabic, some carragheen preparations, chia gum, psyllium, gum tragacanth, ghatti gum, okra gum, some hemicellulose preparations, welan gum, rhamsan gum, gellan gum and certain pectins with a high degree of esterification are suitable as such, but much more preferentially in the hydrolysed form or shortened form obtained in some other way.
When polysaccharides contain too many negatively charged groups, such as, for example, alginates, some carragheen preparations, gellan gum, xanthan gum, karaya gum and many pectin preparations, the suitable quantity of negatively charged groups can be obtained by protecting a suitable fraction of these negatively charged groups, for example by esterification. By this means the specific interaction with the tight junctions can be increased.
Preferably, polysaccharides containing 1 carboxyl group per 10 to 10,000 saccharide units are used. A carboxydextran having a molecular weight of 20 to 2,000 kD and containing 1 carboxyl group per 10 to 10,000 saccharide units is particularly preferred.
The polysaccharides are preferably present in the preparation in a quantity such that the concentration of these polysaccharides in the intestines is 0.1 to 20 g/l, preferably 0.5 to 10 g/l, and most preferentially 1 to 6 g/l. The minimum quantity of the active substance is determined in that a significant decrease in the transport through the tight junctions is observed.
It is not necessary for the polysaccharides to be administered at that location where paracellular transport is disturbed. The presence of the active component at a location somewhere in the intestines between the stomach and the affected location is adequate.
Some of the polysaccharides used according to the invention have a viscosity-raising effect, which could prevent the absorption of nutritional components. The preparation must have a composition such that the normal transcellular transport is not impeded.
More particularly, the nutritional composition according to the invention has a viscosity of less than 100 mPaxc2x7s, preferably less than 40 and even more preferentially less than 30 mPaxc2x7s. For the present invention it is important, in particular, that the polysaccharides, irrespective of the other constituents of the composition, have only a slight viscosity-raising effect. The viscosity-raising effect of the active polysaccharides in the composition must be less than 20 and preferably less than 10 mPa.s and can be, for example, 3 mPaxc2x7s. The viscosity of the product is thus in the main caused by components in the product other than the polysaccharides.
The viscosity is determined by means of a Carri-med at a shear rate of 100 per second and at 20xc2x0 C.
In the case of dry products the viscosity limits described above apply after reconstitution of the product.
In general, therefore, the type of polysaccharide (structure and molecular weight) and the concentration thereof will be so chosen that an optimum combination of effectiveness and viscosity is obtained. Not only molecular size, but also degree of branching and degree of loading determine activity, viscosity and/or fermentation behaviour.
The polysaccharides according to the invention prevent the free transport of high molecular weight substances, allergens and microorganisms through the tight junctions of the intestinal wall. In this context high molecular weight substances are understood to be the substances which under normal conditions are not able to pass through the tight junctions and for which a toxic or allergenic action can be assumed. These substances will in general have a molecular size of more than 4,000 Dalton. Antigens, substances which activate the immune system, are in general peptides, which may or may not be glycosidated, often with a molecular weight in excess of 10,000 Dalton. Allergens are antigens which give rise to an allergic reaction, which is usually mediated via immunoglobulin E.
In this context microorganisms are understood to be in particular microorganisms which occur in the intestinal lumen. Thus, for example, under certain conditions overgrowth of microorganisms in the small intestine can take place, as a result of which tight junctions are exposed to these microorganisms to an increased extent.
According to another aspect of the invention, foods or preparations are proposed which contain these slightly negatively charged, non-digestible polysaccharides. These foods can be:
complete foods;
food supplements;
health-promoting preparations; and
tube feeds.
The compositions according to the invention can be used to prevent or to treat allergies, allergic reactions, sepsis and inflammatory processes, such as those which can arise under emotional and physical stress, ischaemia, reperfusion damage during and after operations, following radiation treatment and/or chemotherapy of cancer patients and in the case of inflammatory intestinal diseases, diarrhoea and allergies.
The complete foods and food supplements described above can, in particular, be used for the treatment or prevention of inflammatory intestinal diseases, such as colitis ulcerosa, inflammatory bowel disease and Crohn""s disease. Specific other constituents which can be incorporated in such foods and supplements are growth hormones, glutamines, n-3 LCPUFA""s and the requisite contents of macro- and micro-ingredients.
Furthermore, the foods according to the invention can be used before and after operations. Specifically, ischaemia and reperfusion damage to the intestines often occurs during operations, as a result of which the tight junctions open. Introducing the polysaccharides according to the invention into the intestines before and after the operation could prevent uncontrolled paracellular transport. The administration of these polysaccharides can also be beneficial following chemotherapy.
In the case of diarrhoea a number of patho-morphological changes can also occur which are associated with increased permeability of the tight junctions. These changes can occur both in the case of travellers"" diarrhoea and after diarrhoea following treatment with antibiotics and diarrhoea which follows after food poisoning. The complete foods and food supplements according to the invention can be used to counteract the adverse consequences of this increased permeability.
The tight junctions can also open during stress, both of a physical nature (for example endurance sports) and of an emotional nature, as a result of which bacterial translocation takes place. An example of emotional stress under which this takes place is the stress which occurs during the transport of pigs to the slaughterhouse. Contamination of the meat can occur as a result. Another example is the stress which occurs when weaning piglets. The polysaccharides can be administered before, during or after stress.
With the aid of the polysaccharides according to the invention it is also possible to prepare preparations which are suitable for patients who have a food allergy, such as an allergy to cow""s milk or to gluten. The increase in the permeability as a result of exposure to the allergen can be prevented. These preparations are formulated such that the said allergens are not present therein.